Braking unit for Altivar 61/71 drives
The VW3A7E102 is a resistance braking unit designed for Schneider Electric Altivar 61 and 71 variable speed drives, rated for drives up to 400 kW continuous power. Its maximum permanent braking power is 750 kW at 400 V, meaning it can safely dissipate regenerative energy from a decelerating motor load at that peak rate — essential for applications like centrifuges, winders, or high-inertia conveyors where the drive cannot absorb the braking energy internally.
Braking capacity and resistor selection
The unit engages at a DC bus voltage threshold of 785 V DC ±1 %, with a maximum DC bus voltage of 850 V — the chopper circuit switches the external resistor across the bus when the voltage rises above the threshold, preventing an overvoltage trip on the drive. The minimum resistor value to associate is 0.7 Ohm; selecting a resistor below this value risks overcurrent in the chopper IGBT, while a higher value reduces braking torque. The load factor varies with power: 15 % at 550 kW, 5 % at 750 kW, and 50 % at 440 kW, all at constant power and at the engage threshold — this duty cycle governs the resistor's thermal sizing, not just the peak power. Thermal losses are 750 W, dissipated as heat inside the enclosure; the unit requires 600 m³/h of cooling air volume to maintain the -10 to 50 °C operating ambient range.
Installation environment and protection
The unit is protected by an integrated thermal probe that monitors the heatsink temperature, and it must be mounted vertically per the operating position specification. Operating altitude is limited to 2000 m without derating. Vibration resistance is rated at 0.2 gn — the unit should be mounted on a rigid panel or backplate in the drive cabinet, not on a vibrating machine frame.
Obsolete — sourcing through independent channels
Schneider Electric has marked the VW3A7E102 as obsolete. The unit is available through independent surplus and broker channels. Quantities are lot-specific and confirmed at the time of RFQ.